Field
The disclosed concept pertains generally to electrical distribution systems having a number of circuit protection devices, such as circuit breakers having configurable electronic trip units, and, more particularly, to a system for detecting faults in such an electrical system distribution and locating the zones where the faults occurred.
Background Information
Circuit interrupters, such as for example and without limitation, circuit breakers, are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition, a short circuit, or another fault condition, such as an arc fault or a ground fault. Molded case circuit breakers (MCCBs) typically include a pair of separable contacts per phase. The separable contacts may be operated either manually by way of a handle disposed on the outside of the case or automatically in response to a detected fault condition. Typically, such circuit breakers include an operating mechanism, which is designed to rapidly open and close the separable contacts, and a trip mechanism, such as a trip unit, which senses a number of fault conditions to trip the breaker automatically. Upon sensing a fault condition, the trip unit trips the operating mechanism to a trip state, which moves the separable contacts to their open position.
Typically, in a power distribution system, two or more circuit interrupters will be positioned between a load and the source of the fault current. In order to minimize electrical service interruption, the circuit interrupters are selective in response to the fault such that the one upstream and nearest the fault will first attempt to interrupt the fault current. If this circuit interrupter does not timely clear the fault, then the next upstream circuit interrupter will attempt to do so, and so on. This response selectivity is sometimes termed system selective coordination.
However, when a short circuit occurs in a power distribution system, it can be difficult to achieve selective coordination among circuit interrupters. This may lead to either failed isolation of the fault that causes an upstream circuit interrupter to also trip, resulting in broader power outage to a facility or process, or high let through energy due to delayed circuit interruption. Thus, the ability to identify and locate which zone within a power distribution system has a short circuit fault would provide improved coordination, and reduce the time and amount of energy dissipated in the electrical system and circuit interrupter.